The AvaTax DotNet SDK is available on NuGet:
Manage NuGet Packages
Installto add the latest version
A detailed walkthrough is available on the Avalara Developer Blog
The DotNet SDK uses a fluent interface to define a connection to AvaTax and to make API calls to calculate tax on transactions. Here's an example of how to connect to AvaTax in C#:
The DotNet SDK allows you to capture API requests and responses either using an event hook or by logging all API calls to disk. You can use this feature to capture information about API call errors, or performance statistics, or anything else.